Force applying apparatus

ABSTRACT

The present apparatus is used for applying forces substantially to a point of a structural member, for example, for testing an axle of a motor vehicle by simulated forces corresponding to those applied to the member when it is in actual use. This is accomplished by push rods and force delivering means, such as piston cylinder means. The rods and piston cylinder means are interconnected by yokes in such a way that forces may be applied independently or in various combinations in the three spatial directions, to said point of the structural member.

United States Patent Klinger Random Load Fatigue Test on AutomotiveCom-' FORCE APPLYING APPARATUS Inventor: Friedrich Klinger,Darmstadt-Arheilgen, Germany Assignee: Carl Schenck MaschinenfabrikGmbH, Darmstadt, Germany Filed: Feb. 18, 1971 Appl. No.: 116,529

Foreign Application Priority Data Sept. 30, 1970 Germany ..P 20 48 050.6

US. Cl ..73/91, 73/100 1111. c1. ..G0ln 3/00 Field of Search....73/88 R,91, 92, 93, 100, 118,

' References Cited OTHER PUBLICATIONS ponents & Structure by J. D. Camp,ASTM-STP, 476, presented in June 1969 '14 1 Oct. 10,1972

Primary Examiner-James J. Gill Assistant ExaminerMarvin SmollarAttomey-W'G. Fasse ABSTRACT The present apparatus is used for applyingforces substantially to a point of a structural member, for example, fortesting an axle of a motor vehicle by simulated forces corresponding tothose applied to the member when it is in actual use. This isaccomplished by push rods and force delivering means, such as pistoncylinder means. The rods and piston cylinder means are interconnected byyokes in such a way that forces may be applied independently or invarious combinations in the three spatial directions, to said point ofthe structural member.

10 Claims, 3 Drawing Figures I3 IO A PKTENTEDUBI 10 m2 m T N E V WFRIEDRICH KLINGER ATTORNEY FORCE APPLYING APPARATUS BACKGROUND OF THEINVENTION structural members under simulated conditions which correspondto those of the actual use of such members which are subject tosuperimposed variable forces in all three dimensional directions such asvehicles, or more specifically, vehicular axles.

For testing motor vehicles or motor vehicle parts, especially motorvehicle axles, it is desirable to simulate the stress and strainconditions on the testing stand as truly and as genuinely as possible inorder to recreate the actual operating conditions as they occur in thepractical or actual operation of the vehicle in order to ascertain thebehavior of the material and the influences or the characteristics ofthe structure being tested, especially under durability test conditionsfor ascertaining said behavior and influences for a longtime operation.

in connection with motor vehicles, the loads which are transferred bythe wheel to the axle are essentially effective in three spatialdirections. Thus, the shocks resulting from the profile of the roadsurface are effective substantially in a vertical direction, forexample, when the vehicle passes over an undulation in the road surface.Other forces are effective in parallel to the direction of travel, thatis, they are effective essentially in the horizontal direction. Theseforces are caused, for example, by the friction between the wheels andthe road or by the air resistance or drag as well as by the braking orby the acceleration. Further forces are cfprior to the application of aload to the axle. Such displacement changes the forces which are appliedto the vehicle axle by the two other piston cylinder arrangements.Accordingly, it is necessary to ascertain the forces or rather thechanges in the forces which result due to the spatial displacement ofthe vehicle axle being tested in order to correctly apply predeterminedloads to the axle. Such changes must be ascertained by computation andthe changes must be taken into account for applying the testing forces.Thus, it will be appreciated that such devices require a largeinvestment in electronic equipment in addition to the testing equipmentproper.

It has also been suggested, to combine the three hydraulic pistoncylinder arrangements in a compact unit in such a manner that a memberof a sliding joint or coupling is rigidly connected with one of thethree hydraulic cylinders, whereby said one member may be displaced inspace in its longitudinal direction. The two other hydraulic pistoncylinder means are arranged in such a manner that they are capable ofdisplacing the fective across the direction of travel, for example, the

centrifugal forces resulting when the vehicle negotiates a curve orlateral shocks which occur when the vehicle travels over or against acurbstone are effective in a lateral direction perpendicularly to thedirection of travel.

For simulating the above stress or load conditions in a testing stand inwhich the forces are applied to the vehicle or rather to the vehicleaxle by means of hydraulic piston cylinder arrangements it is necessaryto provide three such piston cylinder arrangements which are effectiveindependently in three different directions.

Heretofore, an apparatus of the above type has been proposed in whichthe hydraulic cylinders have been arranged separately of each other inthe three spatial directions about the vehicle axle to be tested. Thesedevices have the disadvantage that the testing stand requires a verylarge space due to the just mentioned type of construction. A furtherdisadvantage is seen in that the push or piston rods of the hydraulicpiston cylinder arrangement have a limited length. As a result of theforce applied by one of the cylinders to the vehicle axle presentlybeing tested, such axle is displaced in space to a point other than thatoccupied by the axle other member of said sliding joint or coupling indifferent lateral directions. A drawback of this conventional apparatusis seen in that the necessary shifting joints or couplings are rathercomplicated and involved as well as expensive.

OBJECTS OF THE INVENTION In view of the foregoing, the invention aims atachieving the following objects, singly or in combination:

to overcome the outlined drawbacks;

to provide an apparatus capable of applying forces or deformations to apoint from three different spatial directions, whereby such forces ordeformations are to be applied independently or singly as well as invarious combinations;

to provide a testing apparatus of compact construction for testingstructural members under simulated operating conditions which are very'much alike to the stress and load conditions under which suchstructural members will be operated in actual use, especially vehicleaxles, aircraft parts, and any structural members which in their actualuse are subject to superimposed forces;

to provide a durability testing apparatus for structural members whichwill permit maintaining the structural member being tested in the sameposition throughout the testing operation;

to avoid expensive and complicated slidable joints or slidable couplingmeans; and

to arrange the necessary force delivering means and push rods in such amanner relative to each other that a compact structure will result whichrequires substantially less space than heretofore.

SUMMARY OF THE INVENTION According to the invention there is provided aforce applying apparatus, especially for testing structural members suchas vehicular axles, wherein one push rod of a piston cylinderarrangement carries a forked yoke which in turn carries in its forkedends a second push rod of a second piston cylinder arrangement. A thirdpush'rod of a third piston cylinder arrangement is supported in afurther yoke, whereby the second and third push rods are interconnectedwith each other at an angle and the further yoke is connected with thestructural member to which the forces are to be applied. The elementsare so supported that a point of intersection between the second andthird push rod is displaceable relative to the two yokes.

Preferably, hydraulic piston cylinder arrangements are employed inaccordance with the present invention.

BRIEF FIGURE DESCRIPTION In order that the invention may be clearlyunderstood, it will now be described, by way of example, with referenceto the accompanying drawings, wherein:

FIG. 1 is a perspective view of one embodiment of the present inventionillustrating its generic concept;

FIG. 2 is a diagrammatic perspective view similar to that of FIG. 1 butillustrating a modified embodiment of the present invention; and

FIG. 3 is a sectional view along line 3-3 in FIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION:

FIG. 1 shows a first force delivering means such as a piston cylinderarrangement 1 which is supported in a frame or foundation structuresymbolically shown in FIGS. 1 and 2 and forming a force reaction point.A push rod or piston 2 is movable by the piston cylinder arrangement 1vertically up and down as indicated by the arrow 3. The push rod 2 isalso rotatable as indicated by the arrow 4 and as will be explained insomewhat more detail with reference to FIG. 3.

To the upper or outer end of the push rod 2 there is rigidly attached anintermediate yoke 5, for example by screws 6. The intermediate yoke 5has forked ends 7 and 8 carrying bearings 9 and 10 respectively. Asecond force delivering means, such as a piston cylinder arrangement 11is rigidly connected to one end 8 of the yoke 5, for example, by aweldment 12. The second piston cylinder arrangement 11 actuates a secondpush rod 13 which is supported for axial movement in the bearings 9 and10 as indicated by the arrow 14. As mentioned, the second push rod 13 ismovable back and forth along the axis AA. For this purpose, the pistoncylinder arrangement 11 is connected through a conduit 15 to a source ofhydraulic power not shown.

A third push rod 16 is supported in a power applying yoke 17 in such amanner that the second push rod 13 and the third push rod 16 form apoint of intersection 18. Accordingly, the push rods are arranged sothat they cross each other at an angle, preferably at an angle of 90.Means 19 are provided for interconnecting the push rods 16 and 13. Suchinterconnecting means will be described in more detail below.

A third force delivering means, such as a piston cylinder arrangement 20is provided for axially moving either the push rod 16 or the forceapplying yoke 17 together with its force transmitting member 21 which isrigidly connected to the yoke 17 on the one hand and which is releasablyconnected to the structural member 22, for example, in the form of avehicle wheel, by means of bolts 23 and nuts not shown.

In the embodiment of FIG. 1 the second push rod 13 and the third pushrod 16 are rigidly connected to each other by the connection means 19which may be a cross bushing into which the push rods are inserted witha press fit. It is also possible to interconnect the push rods with thecross bushing and weldments 24. The force delivering yoke 17 issupported at both ends on the third push rod 16 by bearings similar tobearings 9, 10 mentioned above. for axial movement as indicated by thearrow 25 as well as for rotational movement as indicated by the arrow26. Also in this embodiment the third hydraulic drive means 20 arerigidly connected to one end of the yoke 17 as by a weldment 27 so thatthe yoke 17 and drive means 20 move in unison relative to the push rod16. Such movement is accomplished by the supply of a fluid underpressure through a conduit 28 as, per se, is well known in the art.Incidentally, the first piston cylinder arrangement 1 is also connectedto a source of pressure.

In view of the foregoing, it will be appreciated that a vertical forceis applied to the structural member 22 by moving the first push rod 2 upand down, whereby the force is transmitted through the yoke 5 t0 thesecond push rod 13 from there to the third push rod 16 and from there tothe yoke 17 and transmittal member 21 to the structural member 22. Aforce in a first lateral direction is applied through the push rod 13and the push rod 16, whereas a further force in a lateral direction isapplied by moving the yoke 17 relative to the push rod 16 which is fixedto the push rod 13.

FIG. 2 illustrates a slightly modified embodiment as compared to FIG. 1.However, the same elements are identified by the same reference numeralsso that their repeated description is not necessary. The axis AA hasbeen rotated to simplify the illustration. In this embodiment the secondpush rod 13 is still supported in the forked ends 7 and 8 of theintermediate yoke 5 or in the ends 7 and in the piston cylinderarrangement 11 if the latter is considered to form a structural unitwith the end 8 of the yoke 5. However, the push rod 13 is provided witha sleeve or bushing 29 located approximately intermediate the supportingmeans for the push rod 13. The bushing 29 is rigidly connected to thethird piston cylinder arrangement 20, for example, by a rigid rod 30.Rather than driving the yoke 17 as in FIG. 1, the piston cylinderarrangement 20 now drives the push rod 16 which is freely movable in itsaxial direction through the bushing 29 and since the ends of the yoke 17are now rigidly connected to the push rod 16, for example, by weldments31 and 32, the movement of the push rod 16 is transmitted through theyoke 17 to the structural member 22.

In order to control the power or pressure supply to the piston cylinderarrangements 1, 11, and 20 there are provided according to the inventionforce or deformation sensing means which may be provided in the form ofdistance measuring strips 33 glued to the push rods 2, 13, and 16 asindicated and covered by a protective sleeve 34 as shown. These sensingstrips function on the basis of the fact that a push rod will beslightly elongated or slightly upset. Such elongation or upsetting willbe registered or measured by these so called expansion strips. Since thelength of the expansion strip is known and since the elasticitycoefficient of the push .rods is given, simple conclusions can be madewith regard to the force transmitted by the push rod or through the pushrod. Such expansion strips for ascertaining transmitted forces are wellknown in the art as well as electronic circuitry responsive to suchexpansion strips for control purposes.

The expansion sensing strips may be replaced by distance measuringelements operating'on the basis of measuring a resistance, acapacitance, or an inductance variation. These distance measuringdevices are also well known in the art.

FIG. 3 simply illustrates that there is a loose fit 35 between thecylinder housing 1 and the piston 36 so as to permit rotational movementof the respective piston rod 2. This applies also with regard to theother piston cylinder arrangements 11 and 20.

Making the push rods, especially the push rods 2 and 16 rotatabletogether with their respective yokes 5 and 17, relative to therespective cylinders has the further advantage that the structuralmember may be rotated during the testing. This may become necessary, forexample, when the front axle of a motor vehicle is to be tested becausethe front axle is, in addition to the above mentioned forces, alsosubject to rotational forces which result due to the steering of themotor vehicle. Providing this special testing feature according to theinvention constitutes a substantial advance in the art.

Although specific embodiments have been described, it is to beunderstood that the invention comprises all modifications andequivalents within the scope within the appended claims.

What I claim is:

1. An apparatus for applying forces substantially to a point of astructural member, said forces being variable in three spatialdirections comprising a force reaction point, a first push rod connectedto said force reaction point, first force delivering means operativelyconnected to said first push rod for moving the first push rod, anintermediate yoke rigidly attached to said first push rod, first bearingmeans carried by said intermediate yoke, a second push rod supported inthe first bearing means, second force delivering means operativelyconnected to said second push rod for moving the second push rod, athird push rod, a third force delivering means operatively connected tosaid third push rod, a force applying yoke, second bearing means carriedby the force applying yoke, said third push rod being supported in saidsecond bearing means, means for interconnecting the second and thirdpush rods with each other at an angle to form a point of intersectionbetween the second and third push rods, whereby said point ofintersection is movable relative to said intermediate yoke, and saidforce applying yoke is movable relative to said point of intersection,and means for connecting the force applying yoke to said structuralmember.

2. The apparatus according to claim 1, wherein said means forinterconnecting the second and third push rods comprise cross connectionmeans for rigidly interconnecting the second and third push rods, saidapparatus further comprising means for rigidly interconnecting the thirdforce delivering means and the force delivering yoke, and means foraxially displacing the third force delivering means relative to thethird push rod.

3. The apparatus according to claim 1, further comprising means forrigidly interconnecting the force delivering yoke with said third pushrod, sleeve means rigidly connected to the second push rod and arrangedto receive the third push rod in said sleeve means, whereby the thirdpush rod is movable axially in said sleeve, and means for rigidlyconnecting said sleeve means to the third force deliverin ean 4. Theapparatus according to cfiim wherein said sleeve means are locatedapproximately intermediate said first bearing means carried by saidintermediate yoke.

5. The apparatus according to claim 1, further comprising force sensingmeans located in suitable positions in said apparatus for measuring theforces delivered to said structural member.

6. The apparatus according to claim 1, further comprising deformationsensing means located in suitable positions in said apparatus formeasuring deformations resulting from said forces.

7. The apparatus according to claim 1, wherein said push rods are pistonrods and said force delivering means are piston cylinder means.

8. The apparatus according to claim 7, wherein said force deliveringmeans are hydraulic piston cylinder means.

9. The apparatus to claim 7, wherein said force delivering means arepneumatic force delivering means.

10. The apparatus according to claim 1, wherein the structural member isa part of a craft, especially a motor vehicle.

1. An apparatus for applying forces substantially to a point of astructural member, said forces being variable in three spatialdirections comprising a force reaction point, a first push rod connectedto said force reaction point, first force delivering means operativelyconnected to said first push rod for moving the first push rod, anintermediate yoke rigidly attached to said first push rod, first bearingmEans carried by said intermediate yoke, a second push rod supported inthe first bearing means, second force delivering means operativelyconnected to said second push rod for moving the second push rod, athird push rod, a third force delivering means operatively connected tosaid third push rod, a force applying yoke, second bearing means carriedby the force applying yoke, said third push rod being supported in saidsecond bearing means, means for interconnecting the second and thirdpush rods with each other at an angle to form a point of intersectionbetween the second and third push rods, whereby said point ofintersection is movable relative to said intermediate yoke, and saidforce applying yoke is movable relative to said point of intersection,and means for connecting the force applying yoke to said structuralmember.
 2. The apparatus according to claim 1, wherein said means forinterconnecting the second and third push rods comprise cross connectionmeans for rigidly interconnecting the second and third push rods, saidapparatus further comprising means for rigidly interconnecting the thirdforce delivering means and the force delivering yoke, and means foraxially displacing the third force delivering means relative to thethird push rod.
 3. The apparatus according to claim 1, furthercomprising means for rigidly interconnecting the force delivering yokewith said third push rod, sleeve means rigidly connected to the secondpush rod and arranged to receive the third push rod in said sleevemeans, whereby the third push rod is movable axially in said sleeve, andmeans for rigidly connecting said sleeve means to the third forcedelivering means.
 4. The apparatus according to claim 3, wherein saidsleeve means are located approximately intermediate said first bearingmeans carried by said intermediate yoke.
 5. The apparatus according toclaim 1, further comprising force sensing means located in suitablepositions in said apparatus for measuring the forces delivered to saidstructural member.
 6. The apparatus according to claim 1, furthercomprising deformation sensing means located in suitable positions insaid apparatus for measuring deformations resulting from said forces. 7.The apparatus according to claim 1, wherein said push rods are pistonrods and said force delivering means are piston cylinder means.
 8. Theapparatus according to claim 7, wherein said force delivering means arehydraulic piston cylinder means.
 9. The apparatus to claim 7, whereinsaid force delivering means are pneumatic force delivering means. 10.The apparatus according to claim 1, wherein the structural member is apart of a craft, especially a motor vehicle.